JP6451983B2 - Moisture-cure polyurethane hot melt adhesive and binding adhesive - Google Patents

Description

  The present invention relates to a moisture curable polyurethane hot melt adhesive that can be particularly suitably used as a binding adhesive.

  Binding adhesives are widely used for bonding paper sheets used for bookbinding to cover sheets, and include EVA (ethylene-vinyl acetate copolymer) adhesives and moisture-curable polyurethane hot melt adhesives (RHM). ) Account for the majority.

  However, the EVA adhesives known so far require the coating film to be thick in order to exhibit satisfactory adhesive strength, and as a result, there is a problem that the spreadability of bookbinding is poor.

  On the other hand, conventional moisture-cure polyurethane hot melt adhesives have high viscosity, and when applied at high speed, the adhesive overflows or scatters from the glue box, or is low in viscosity but hard, and both are suitable for high-speed application. None of them satisfied the cutting suitability and spreadability. In addition, since the conventional moisture-curable polyurethane hot melt adhesive has low initial strength, there is a problem that when binding a heavy book, the adhesive layer is deformed in the transport process and the paper sheet is displaced.

JP 2000-225782 A

  The problem to be solved by the present invention is to provide a moisture curable polyurethane hot melt adhesive that is excellent in high-speed coating suitability, cutting suitability, spreadability, initial strength, and bookbinding strength.

  The present invention relates to a polyol (A) containing a crystalline polyester polyol (a-1), a polyether polyol (a-2), an acrylic polyol (a-3) and a polycaprolactone polyol (a-4) and a polyisocyanate ( B) a urethane prepolymer having an isocyanate group obtained by reacting with B), a moisture curable polyurethane hot melt adhesive, and the moisture curable polyurethane hot melt adhesive The present invention relates to an adhesive for bookbinding.

  The moisture-curable polyurethane hot melt adhesive of the present invention is excellent in high-speed application suitability, cutting suitability, spreadability, initial strength, and bookbinding strength. Therefore, the moisture-curable polyurethane hot melt adhesive of the present invention is very suitable as a so-called bookbinding adhesive for bonding a paper sheet and a cover. Further, the moisture-curable polyurethane hot melt adhesive of the present invention has an excellent initial strength, and is therefore suitable for bookbinding heavy books. In addition, the moisture-curable polyurethane hot melt adhesive of the present invention also has an appropriate open time (applicable time), and is used not only for bookbinding but also for fiber bonding / building material lamination and optical member bonding. Also, it can be suitably used.

  The moisture-curable polyurethane hot melt adhesive of the present invention contains a crystalline polyester polyol (a-1), a polyether polyol (a-2), an acrylic polyol (a-3), and a polycaprolactone polyol (a-4). It contains a urethane prepolymer having an isocyanate group obtained by reacting the polyol (A) with the polyisocyanate (B).

  The crystalline polyester polyol (a-1) is an essential component for obtaining excellent binding strength, initial hardness, flexibility and low viscosity, for example, a compound having a hydroxyl group and a polybasic acid are reacted. Things can be used. In the present invention, “crystallinity” means that the peak of crystallization heat or heat of fusion can be confirmed in DSC (Differential Scanning Calorimetry) measurement based on JISK7121: 2012. Indicates that the peak cannot be confirmed.

  Examples of the compound having a hydroxyl group include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, trimethylolpropane, trimethylolethane, and glycerin. Can do. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use butanediol, hexanediol, octanediol, and decanediol from the viewpoint of improving crystallinity and further improving adhesive strength.

  Examples of the polybasic acid include oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, and dodecanedioic acid. These polybasic acids may be used alone or in combination of two or more.

  The number average molecular weight of the crystalline polyester polyol (a-1) is preferably in the range of 500 to 10,000, more preferably in the range of 1,000 to 8,000, from the viewpoint that the open time and bookbinding strength can be further improved. Is more preferable. In addition, the number average molecular weight of the said crystalline polyester polyol (a-1) shows the value measured on condition of the following by gel permeation chromatography (GPC) method.

Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection amount: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4 mass%)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

  The polyether polyol (a-2) is an essential component for obtaining excellent binding strength, film flexibility and low viscosity. For example, polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, ethylene oxide. Modified polypropylene glycol or the like can be used. These polyether polyols may be used alone or in combination of two or more.

  The number average molecular weight of the polyether polyol (a-2) is preferably in the range of 200 to 10,000 from the viewpoint of further improving the bookbinding strength, film flexibility and low viscosity, A range of 000 is more preferred. In addition, the number average molecular weight of the said polyether polyol (a-2) shows the value measured similarly to the number average molecular weight of the said crystalline polyester polyol (a-1).

  As content of the said polyether polyol (a-2), 20 points with respect to 100 mass parts of said crystalline polyester polyol (a-1) from the point which can improve bookbinding intensity | strength, film | membrane flexibility, and a low viscosity further. It is preferable that it is the range of -300 mass parts, The range of 40-200 mass parts is more preferable, The range of 60-150 mass parts is still more preferable.

  The acrylic polyol (a-3) is an essential component for obtaining excellent initial strength, and is obtained, for example, by polymerizing a (meth) acrylic compound containing a (meth) acrylic compound having a hydroxyl group as an essential component. It is. In the present invention, “(meth) acrylic compound” indicates a methacrylic compound and / or acrylic compound, “(meth) acrylate” indicates methacrylate and / or acrylate, and “(meth) acrylic acid” And methacrylic acid and / or acrylic acid.

  Examples of the (meth) acrylic compound having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol tetra (meth). ) Acrylate or the like can be used. These compounds may be used alone or in combination of two or more.

  Examples of other (meth) acrylic compounds include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and tert-butyl (meth). Acrylate, neopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cetyl (meth) acrylate, lauryl (meth) acrylate, etc. (Meth) acrylic acid alkyl ester (meth) acrylic acid alkyl ester; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, 1H, 1H, 5H -Octaf (Meth) acrylic compounds having fluorine atoms such as olopentyl (meth) acrylate and 2- (perfluorooctyl) ethyl (meth) acrylate; isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, sidiclopentanyl (meth) acrylate (Meth) acrylic compounds having an alicyclic structure such as dicyclopentenyloxyethyl (meth) acrylate; polyethylene glycol mono (meth) acrylate, methoxyethyl (meth) acrylate, methoxybutyl (meth) acrylate, methoxytriethylene glycol ( (Meth) acrylic compounds having an ether group such as meth) acrylate and methoxypolyethylene glycol (meth) acrylate; benzyl (meth) acrylate, 2-ethyl-2-methyl- [1 3] - dioxolan-4-yl - methyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, etc. can be used. These (meth) acrylic compounds may be used alone or in combination of two or more. Among these, it is preferable to use the (meth) acrylic compound having the hydroxyl group and the (meth) acrylic acid alkyl ester from the point that the open time and the adhesive strength can be further improved, and 2-hydroxyethyl (meth) acrylate, It is preferable to use one or more (meth) acrylic compounds selected from the group consisting of methyl (meth) acrylate and n-butyl (meth) acrylate.

  The number average molecular weight of the acrylic polyol (a-3) is preferably in the range of 5,000 to 50,000 from the viewpoint of further improving the open time and initial strength, and is in the range of 10,000 to 30,000. The range of is more preferable. In addition, the number average molecular weight of the said acrylic polyol (a-3) shows the value measured similarly to the number average molecular weight of the said crystalline polyester polyol (a-1).

  The glass transition temperature of the acrylic polyol (a-3) is preferably in the range of 30 to 120 ° C, more preferably in the range of 50 to 80 ° C, from the viewpoint that the open time and the initial strength can be further improved. In addition, the glass transition temperature of the said acrylic polyol (a-3) shows the value measured similarly to the glass transition temperature of the said crystalline polyester polyol (a-1).

  As the usage-amount of the said acrylic polyol (a-3), it is 1-80 mass parts with respect to 100 mass parts of said crystalline polyester polyol (a-1) from the point which can improve an open time and initial stage strength further. The range is preferably 3 to 30 parts by mass, and more preferably 5 to 30 parts by mass.

  The polycaprolactone polyol (a-4) is an essential component for obtaining excellent initial strength. For example, a product obtained by reacting the above-mentioned compound having a hydroxyl group with ε-caprolactone can be used.

  The number average molecular weight of the polycaprolactone polyol (a-4) is preferably in the range of 5,000 to 200,000 from the viewpoint that the open time and the initial strength can be further improved. A range of 000 is more preferred.

  As a usage-amount of the said polycaprolactone polyol (a-4), it is 1-100 mass parts with respect to 100 mass parts of said crystalline polyester polyol (a-1) from the point which can improve an open time and initial stage strength further. The range is preferably 3 to 50 parts by mass.

  The polyol (A) contains a crystalline polyester polyol (a-1), a polyether polyol (a-2), an acrylic polyol (a-3) and a polycaprolactone polyol (a-4). You may contain another polyol as needed.

  As said other polyol, an amorphous polyester polyol, polybutadiene polyol, polyisoprene polyol etc. can be used, for example. These polyols may be used alone or in combination of two or more.

  Examples of the polyisocyanate (B) include aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate , Cycloaliphatic diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, or other aliphatic or alicyclic polyisocyanates. These polyisocyanates may be used alone or in combination of two or more. Among these, aromatic polyisocyanate is preferably used from the viewpoint of reactivity and adhesive strength, and diphenylmethane diisocyanate is more preferably used.

  The urethane prepolymer is obtained by reacting the polyol (A) and the polyisocyanate (B), and reacts with moisture present in the air or in the base material to which the urethane prepolymer is applied. It has an isocyanate group capable of forming a crosslinked structure.

  As a method for producing the urethane prepolymer, for example, a mixture of the polyol (A) is dropped into a reaction vessel containing the polyisocyanate (B) and then heated, and the isocyanate group of the polyisocyanate (B) is changed. , And can be produced by reacting under an excess condition with respect to the hydroxyl group of the polyol (A).

  When producing the urethane prepolymer, the equivalent ratio of the isocyanate group of the polyisocyanate (B) to the hydroxyl group of the polyol (A) (isocyanate group / hydroxyl group) further improves the adhesive strength and flexibility. From the point which can be performed, the range of 1.1-5 is preferable, and the range of 1.5-3 is more preferable.

  The isocyanate group content (hereinafter abbreviated as “NCO%”) of the urethane prepolymer obtained by the above method is in the range of 1.7 to 5 from the viewpoint of further improving the adhesive strength. Is preferable, and the range of 1.8-3 is more preferable. In addition, NCO% of the said urethane prepolymer shows the value measured by the potentiometric titration method based on JISK1603-1: 2007.

  The moisture curable polyurethane hot melt adhesive contains the urethane prepolymer, but may contain other additives as necessary.

  Examples of the other additives include a curing catalyst, an antioxidant, a tackifier, a plasticizer, a stabilizer, a filler, a dye, a pigment, a fluorescent brightening agent, a silane coupling agent, a wax, and a thermoplastic resin. Can be used. These additives may be used alone or in combination of two or more.

  The melt viscosity at 120 ° C. when the moisture-curable polyurethane hot melt adhesive of the present invention obtained by the above method is measured with a cone plate viscometer is 1 in terms of high-speed coating suitability, cutting suitability, and bookbinding strength. The range is preferably from 1,000 to 10,000 mPa · s, more preferably from 2,000 to 9,000 mPa · s, and still more preferably from 3,000 to 8,000 mPa · s. In addition, the measuring method of the said melt viscosity is described in detail in the Example mentioned later.

  The moisture curing type polyurethane hot-melt adhesive is preferably 20 or more from the viewpoint of high-speed application suitability, cutting suitability, and bookbinding strength as the JISA hardness after being applied in a 23 ° C. atmosphere and allowed to stand for 30 minutes. The range of 25-90 is more preferable, and the range of 30-80 is still more preferable. In addition, the measuring method of the said JISA hardness is described in detail in the Example mentioned later.

  The moisture curing type polyurethane hot melt adhesive was applied in a 23 ° C. atmosphere, allowed to stand for 30 minutes, and further allowed to stand in a 23 ° C., 50% humidity atmosphere for 1 week. From this point, it is preferably 95 or less, and more preferably in the range of 50 to 90. In addition, the measuring method of the said JISA hardness is described in detail in the Example mentioned later.

  The upper yield point stress of the cured film of the moisture curable polyurethane hot melt adhesive is preferably 7 MPa or less, more preferably in the range of 3 to 6 MPa, from the viewpoint of book spread. In addition, the measuring method of the said upper yield point stress is described in detail in the Example mentioned later.

  As described above, the moisture-curable polyurethane hot melt adhesive of the present invention is excellent in high-speed application suitability, cutting suitability, spreadability, initial strength, and bookbinding strength. Therefore, the moisture-curable polyurethane hot melt adhesive of the present invention is very suitable as a so-called bookbinding adhesive for bonding a paper sheet and a cover.

  As a method of binding with the moisture-curable polyurethane hot melt adhesive of the present invention, for example, the adhesive is applied to a bonding surface of a bundle of a plurality of paper sheets and a bonding surface of a cover sheet, and a sheet and a cover sheet are coated. And a method of pasting together.

  Examples of the method for applying the adhesive to the bonding surface include a coater system such as a roll coater, a spray coater, a T-tie coater, a knife coater, and a comma coater; dispenser, inkjet printing, screen printing, offset printing, and the like. A precision method or the like can be used.

  After bonding the paper sheet and the cover, drying and curing are preferably performed by known methods according to the type of adhesive used.

  The thickness of the adhesive layer depending on the adhesive can be appropriately determined within a range of 0.001 to 0.5 cm, for example.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
In a four-necked flask equipped with a stirrer and a thermometer, crystalline polyester polyol-1 (reacted with 1,6-hexanediol and dodecanedioic acid, number average molecular weight; 3,500, hereinafter “crystalline” 30 parts by mass of polypropylene glycol (number average molecular weight; 1,000. Or less, abbreviated as “PPG”), and acrylic polyol (methyl methacrylate, n-butyl methacrylate). And 2-hydroxyethyl methacrylate polymerized, number average molecular weight; 20,000, hereinafter abbreviated as “AcPol”), 5 parts by mass, polycaprolactone polyol (number average molecular weight; 40,000, hereinafter, “ PCL-1 ") is mixed and 10 parts by mass are mixed and heated at 100 ° C under reduced pressure to bring the moisture in the flask to 0.0. It was dehydrated until mass%. After the inside of the flask is cooled to 90 ° C., 19 parts by mass of 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as “MDI”) melted at 70 ° C. is added until the NCO% becomes constant under a nitrogen atmosphere. By making it react at 110 degreeC for about 3 hours, the urethane prepolymer was obtained and the moisture-curable polyurethane hot-melt-adhesive was obtained.

[Example 2]
In a four-necked flask equipped with a stirrer and a thermometer, 35 parts by mass of crystalline PEs-1, 36 parts by mass of PPG, 5 parts by mass of AcPol, polycaprolactone polyol (number average molecular weight; 80,000, hereinafter, “ PCL-2 ").
After cooling the inside of the flask to 90 ° C., 19 parts by mass of MDI melted at 70 ° C. was added, and a urethane prepolymer was obtained by reacting at 110 ° C. for about 3 hours under a nitrogen atmosphere until the NCO% became constant. A curable polyurethane hot melt adhesive was obtained. This moisture curable polyurethane hot melt adhesive was obtained.

[Example 3]
In a four-necked flask equipped with a stirrer and a thermometer, 15 parts by mass of crystalline PEs-1 and crystalline polyester polyol-2 (reaction of 1,6-hexanediol and adipic acid, number average molecular weight; 3,500, hereinafter abbreviated as “crystalline PEs-2”), 15 parts by mass, 36 parts by mass of PPG, 5 parts by mass of AcPol, and 10 parts by mass of PCL-1 were mixed and mixed under reduced pressure at 100 ° C. It dehydrated until it heated and the water | moisture content in a flask became 0.05 mass%.
After cooling the inside of the flask to 90 ° C., 19 parts by mass of MDI melted at 70 ° C. was added, and a urethane prepolymer was obtained by reacting at 110 ° C. for about 3 hours under a nitrogen atmosphere until the NCO% became constant. A curable polyurethane hot melt adhesive was obtained. This moisture curable polyurethane hot melt adhesive was obtained.

[Example 4]
In a four-necked flask equipped with a stirrer and a thermometer, 20 parts by mass of crystalline PEs-1, 15 parts by mass of PEs-2, 36 parts by mass of PPG, 5 parts by mass of AcPol, and 5 parts by mass of PCL-2 The mixture was mixed and heated at 100 ° C. under reduced pressure to dehydrate until the water content in the flask was 0.05 mass%.
After cooling the inside of the flask to 90 ° C., 19 parts by mass of MDI melted at 70 ° C. was added, and a urethane prepolymer was obtained by reacting at 110 ° C. for about 3 hours under a nitrogen atmosphere until the NCO% became constant. A curable polyurethane hot melt adhesive was obtained.

[Comparative Example 1]
A moisture curable polyurethane hot melt adhesive (“Hybon 4852” manufactured by Hitachi Chemical Co., Ltd.) was used.

[Comparative Example 2]
A moisture curable polyurethane hot melt adhesive (“QR3317BR” manufactured by Henkel) was used.

[Measurement method of melt viscosity at 120 ° C.]
After the moisture-curable polyurethane hot melt adhesives obtained in Examples and Comparative Examples were melted at 120 ° C. for 1 hour, 1 ml was sampled and melt viscosity was measured with a cone plate viscometer (40 P cone, rotor rotation speed: 50 rpm). Was measured.

[Measurement method of JISA hardness]
After the moisture-curable polyurethane hot melt adhesive obtained in Examples and Comparative Examples was melted at 120 ° C. for 1 hour, it was poured into a cylindrical mold having a diameter of 56 mm and a height of 8 mm in an atmosphere of 23 ° C., and 30 minutes. The JIS hardness of the surface of the cylindrical molded article after being allowed to stand and the JISA hardness of the surface of the cylindrical molded article after being allowed to stand for one week in an atmosphere of 23 ° C. and 50% humidity were measured in accordance with JIS K7312.

[Measurement method of upper yield stress]
After the moisture-curable polyurethane hot melt adhesives obtained in Examples and Comparative Examples were melted at 120 ° C., an applicator was used so that the thickness after application on a polyethylene terephthalate film subjected to release treatment was 100 μm. And applied. Then, it was left to stand at 23 ° C. and a humidity of 50% for 1 week to obtain a cured film of a moisture curable polyurethane hot melt adhesive. The upper yield point stress (MPa) of the obtained cured film having a thickness of 100 μm was measured according to JIS K7311-1995.

[Evaluation method of high-speed application suitability]
The moisture curable polyurethane hot melt adhesive obtained in Examples and Comparative Examples was melted at 120 ° C., placed between two roll coaters, rotated at a speed of 50 m / min, When the adhesive did not overflow, the high-speed application suitability was evaluated as “T”, and when the adhesive overflowed, it was evaluated as “F”.

[Evaluation method of cutting suitability]
The moisture curable polyurethane hot melt adhesives obtained in Examples and Comparative Examples were melted at 120 ° C. and applied on paper to a thickness of 400 μm using an applicator, and left for 5 minutes and cut with a cutting machine. The blade was visually checked for adhesive residue. The cutting suitability was evaluated as “T” when there was no adhesive residue on the blade, and “F” when there was adhesive residue.

[Evaluation method of initial strength]
After the moisture-curable polyurethane hot melt adhesives obtained in Examples and Comparative Examples were melted at 120 ° C. for 1 hour, they were coated on a 0.25 mm thick cover using an applicator to a thickness of 400 μm. Then, a bundle of 100 sheets of paper (quality paper, 1 sheet thickness; 0.09 mm) was attached to the coated surface, and after 5 minutes, a precision universal testing machine “AG-10NX” manufactured by Shimadzu Corporation was used. Used to measure the adhesive strength (N / 25 mm), and the initial strength was evaluated as follows.
“T”: Adhesive strength is 8 (N / 25 mm) or more.
“F”: Adhesive strength is less than 8 (N / 25 mm).

[How to make bookbinding samples]
After the moisture-curable polyurethane hot melt adhesives obtained in Examples and Comparative Examples were melted at 120 ° C. for 1 hour, they were coated on a 0.25 mm thick cover using an applicator to a thickness of 400 μm. Then, a bundle of 100 sheets of paper (quality paper, 1 sheet thickness; 0.09 mm) was pasted on the coated surface, and then allowed to stand at 23 ° C. and 50% humidity for 2 days, Obtained.

[Evaluation method of spreadability]
The obtained bookbinding sample was opened by hand, and the spreadability was evaluated as follows.
“T”: Even if the book is left after being opened, the book does not close and the paper sheet does not rise.
"F": After opening the book, the book closes when the hand is released.

[Evaluation method of bookbinding strength]
With respect to the obtained bookbinding sample, the adhesive strength (N / 25 mm) was measured using a precision universal testing machine “AG-10NX” manufactured by Shimadzu Corporation, and the bookbinding strength was evaluated as follows.
“T”: Adhesive strength is 30 (N / 25 mm) or more.
“F”: Adhesive strength is less than 30 (N / 25 mm).

  It has been found that the bookbinding adhesive of the present invention is excellent in high-speed coating suitability, cutting suitability, spreadability, initial strength, and bookbinding strength.

  On the other hand, Comparative Example 1 is an embodiment using a commercially available moisture-curable polyurethane hot melt adhesive having a low adhesive strength, but other performance of the product having excellent spreadability was insufficient.

  Further, Comparative Example 2 is an embodiment using a commercially available moisture-curable polyurethane hot melt adhesive having high adhesive strength, but the obtained bookbinding was hard and the spreadability was poor.

Claims (1)

Polyol (A) and poly ( polyester ) containing crystalline polyester polyol (a-1), polyether polyol (a-2), acrylic polyol (a-3) and polycaprolactone polyol (a-4) isocyanate (B) and a bookbinding adhesive comprising moisture vapor-curable polyurethane hot melt adhesive you containing a urethane prepolymer having an isocyanate group obtained by reacting,
The number average molecular weight of the crystalline polyester polyol (a-1) is in the range of 500 to 10,000,
The number average molecular weight of the polyether polyol (a-2) is in the range of 200 to 10,000, and the content of the polyether polyol (a-2) is the crystalline polyester polyol (a-1) 100. The range is 20 to 300 parts by mass with respect to parts by mass,
The acrylic polyol (a-3) has a number average molecular weight in the range of 5,000 to 50,000, the acrylic polyol (a-3) has a glass transition temperature of 30 to 120 ° C., and the acrylic polyol The content of (a-3) is in the range of 1 to 80 parts by mass with respect to 100 parts by mass of the crystalline polyester polyol (a-1).
The number average molecular weight of the polycaprolactone polyol (a-4) is in the range of 5,000 to 200,000, and the content of the polycaprolactone polyol (a-4) is the crystalline polyester polyol (a-1). The binding adhesive characterized by being in the range of 1 to 100 parts by mass with respect to 100 parts by mass .